The goal of this research is to obtain better data on the health effects of relatively low levels of sulfur oxides and respirable particulates. This will involve a prospective study of six sites where random samples of adults and elementary school children will be surveyed by means of standard questionnaires and simple tests of pulmonary $ function. The adults will be resurveyed every three years, and the children every year. Air monitoring will be done at a central station. Indoor and outdoor monitoring will be done, as well as personal sampling in order to develop better estimates of the exposure to the population.